The invention relates to a press drive, for example for deep-drawing, trimming or punch presses and in particular for high-frequency punch presses with at least 500 punch movements per minute (which, as is known, must be specially designed for this purpose). In most cases, only one tool support, as a rule the upper one, is movable in such presses, although in the last analysis it is only the relative movement which is important; for this reason, it would also be possible within the scope of the invention to design both tool supports to be movable.
More particularly, the invention relates to a press drive for tool supports (5, 7) which are displaceable relative to one another, at least one of which can be driven by means of at least two toggle levers (29, 29'; 129, 129'; 229, 229'), each having two dead centers, to which toggle levers (29, 29'; 129, 129'; 229, 229') drive energy can be transmitted from one drive energy carrier in each case by means of at least one rod (4; 104, 104'; 404, 404'; 504, 504'; 604, 604'; 704), one dead center of the toggle levers (29, 29'; 129, 129'; 229, 229') determining the closest approach of the two tool supports (5, 7) which are displaceable relative to one another, the toggle levers (29, 29'; 129, 129'; 229, 229') bending in opposite directions, and the drive energy carriers being synchronized with one another via a synchronizing arrangement.
The drive of a punch press has to meet very particular requirements, since very high precision in the region of less than one hundredth of a millimeter is required, and this requirement also applies in the case of machine parts which--because of their nature--constantly vibrate and in the case of high compressive forces.
For example, "Werkzeugmaschinen" by Charcut/Tschatsch, Hauser-Verlag, 1984, page 290, presents and describes a drive having a crankshaft (the same effect could also be obtained with an eccentric shaft, either in an embodiment with a circular cam or with an orbiform curve) which drive has some advantages in this respect, since the dead center--in general the bottom dead center--determining the closest approach of the tool support is given by the peak of a sine curve, so that small tolerances in the cam adjustment have virtually no effect. However, this known drive did not meet the requirements in some respects. For example, it was not possible to reduce its mass to the desirable extent, since it was necessary to provide a flywheel to provide the necessary punching force. The arrangement of a flywheel furthermore required the use of a controllable coupling, entailing an additional component which sometimes need repairs. Furthermore, limits are imposed on the speed since the drive has to supply full acceleration each time, although part of the drive energy has to be braked again. Finally, this also results in correspondingly-large drive dimensions, which of course means high energy consumption.